Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$79.67	3.656%	$82.5827	$82.58	$82.60	$82.60
Purchase #2	$13.26	9.285%	$14.4912	$14.49	$14.50	$14.50
Purchase #3	$140.81	3.710%	$146.0341	$146.03	$146.05	$146.00
Purchase #4	$32.58	9.824%	$35.7807	$35.78	$35.80	$35.80
Purchase #5	$115.68	6.809%	$123.5567	$123.56	$123.55	$123.60
Purchase #6	$113.69	12.204%	$127.5647	$127.56	$127.55	$127.60
Purchase #7	$27.97	4.634%	$29.2661	$29.27	$29.25	$29.30
7 purchase totals =	$523.66		$559.2762	$559.27	$559.30	$559.40